Folks, for those of you who I hoped to meet
at Sun & Fun this year, its not going to happen.
Story follows:
After the sun broke through the early AM
clouds, I launched at 1000 and found myself with a tail wind
(unbelievable). I started a 500 fpm slow climb to stay under Bravo
airspace and reached 7000 MSL about 20 miles or so on top of a overcast
(clear on the other side), when the fun started.
The first indication was a difference in the
engine sound, then I noticed the EGT on the rear rotor dropping.
#&%^@ spark Plug SAG was my initial thought - but, I had just put in 4
new B9EQV spark plugs the previous day. Then as things continued to
develop (like EGT went to min 1200F) I noticed that the EGT (which
normally only drops 300F) was at effectively zero (or bottom of meter at
1200F). Well, as Tracy has mentioned pulling back on the power
generally helps, so I did - no joy. Tried switching off
primary and secondary injectors (alternatively of course) still no
improvement. By this time I had begun a 180 deg turn (into a now
headwind).
I tried varying the mixture control -
switched fuel tanks in case I picked up bad fuel in one tank (see I do
learn) - fuel pressure was 43 psi (nominal), oil pressure was 70 psi
(nominal), Oil temp was down to 160F, coolant was also down to 160F ( a
bit low). Indicating that perhaps less power was being produced.
The aircraft was now vibrating with the characteristic
one-rotor-running vibration. Altitude was down to 6500 MSL,
but I was making no attempt to hold altitude. Finally can see ground
beneath, home base still 50 miles away. Situation is continuing to
deteriorate, I have increased fuel flow to 14 gph just to maintain 5000
rpm. A fuel flow of below 12 gph and the engine
starts to unwind as if it is going to stop.
Now I noticed that EGT on rotor number one is
coming down to around 1500F. Clearly not Sparkplug SAG.
Because of the high fuel flow I though perhaps I had a fuel problem even
though pressure was OK. I had also switched fuel tanks, just in case
on tank was bad. Engine is clearly losing power progressively.
I still had 6000 MSL and was thinking about getting home, but then decided
that going into the headwind I would have very little glide (ground path)
and there were no airfield down wind of me anywhere within 40
miles.
I decided to divert to Lancaster ,SC airport
(cross wind) as it was the closest and had a 6000 ft runway - plus I could
see it off my left wing. On the way, down I thought about turning
off the engine to preserve any remaining engine power in case I needed it
to make the runway. THEN! I remember saying so many time, that
despite damage - so long as a rotary is RUNNING, it will stay running -
but, if you turned it off you would probably never get it started
again. I quickly switched the injectors back on while the prop was
still windmilling and the engine caught and fired back up.
Actually had 3000 ft when I arrived over the airfield, so would probably
have made it with the engine stopped. Landing was uneventfully and I
turned off on the taxi way with the engine still running. I notice
that it took almost full throttle just to make the aircraft taxing up a
the small incline to the terminal.
Got parked, uncowled and could find no
evidence of anything amiss - but, clearly I was not going any further in
the air this day.
Then I grabbed the prop and pulled it through
- no evidence of compression on any of the six rotor faces!
It will be a day or two before I can get the
engine off and torn down to determine the cause of the problem but here
are my two candidates in no particular order other than the sequence in
which they occurred to me.
THIS IS PRELIMINARY, so stand by for
corrections after I open the engine up.
Candidate one (my initial thought) -
the new style B9EQV spark plugs electrodes stuck too far down into the
combustion chamber and all six apex seals got clipped. However, if
this were the cause, you would have though that my several full
throttle runup the day before Or early in my max power climb it would have
happened. Why did it wait until 70-80 miles down the road - took
that long for heat expansion to elongate the plug sufficiently to clip the
apex seals? Hard to believe, but I guess it possible. These are
colder plugs so would stay cooler longer But, I would have expected
that if this were the cause, the effective would have been immediate or
very soon after take off..
Candidate two. I installed the plastic
plenum several days ago and have had a number or WOT runs on the ground,
but this was the first flight. Recall, thought, I have flown
with plastic plenums for a number of hours on previous iterations of
intake systems (three intakes to be precise). There is a 3/8"
wall of plastic separating the primary and secondary runners inside this
plenum. This wall divides the two runners from each other .
When the TB is wide open the throttle plate edge is at that divider
and parallel to it. To improve airflow I had sanded that
divider at the throttle body to a thinner front edge (a 3/8" blunt
wall would hurt airflow). The thought occurs that
perhaps this had disintegrated and been ingested causing the damage (those
powerful FAW pulses). This would account for the problem not
happening immediately and after the climb to 7000 MSL. I examined
the engine and the exterior surface of the plenum and there was no
evidence of cracks, etc. However, it did not occur to me at the
time, while waiting for the wife to drive 50 minutes to get me, to take
off the air flow tube to examine the internal condition of the
plenum, will do that tomorrow.
Candidate three??? Any other thoughts
before I tear it down and end the mystery??
Oh, to complete the picture with local color,
the local airport manager suggested that I remove my radios - I
asked why? Well it turns out they had theft of such a
week before (just GREAT!). So pulled all the electronic gear, even
took my seat cushions home with me. While removing the radios -
guess who drives up - nope not the wife, yep!, the county's local
detective assigned to the theft case and asks me what I am doing - well,
removing radios, of course. But, all ends well and I don't get
hauled to jail on top of everything else {:>)
So again, my disappointment in not getting to
see many of you down there. Fix it up and fly down Tuesday you
say? Well, even if there were no serious damage to housings or rotor
(I should be so lucky), the guy who sell the apex seal I would use
- is down in Florida - at Sun & Fun I do believe
{:>).
I have already talked with Tracy and
told him of my sparkplug theory, but I now have to give equal (if not more
weight) to disintegrating plenum. But, once again, I am amazed at the
damage a rotary engine will take and continue to produce power. Here
both rotors were damaged -not just one - and yet I could still
manage, at its lowest 3000 rpm) - probably enough power to keep my RV
and me airborne in a long glide to home (but why chance it when
things could get worst). Besides the prospect of having to make a
go-a-round if I misjudged the approach to our narrow 2200 ft runway was
not appealing - 6000ft was better.
Well, like I always say anything that wants
to break on the ground if just fine with me. Any thing that wants to
break in the air - so long as it gets me safely back to an airpatch
(before dying completely) - is also just fine with me.
My story for the day, now where did I put
that bottle of Whiskey?
Best Regards
Ed